Variable Length Imaging Method Using Electronically Registered And Stitched Single-Pass Imaging

ABSTRACT

An imaging method for generating a substantially one-dimensional scan line image using multiple spatial light modulators, to modulate a homogenous light field, and then anamorphically imaging and concentrating the modulated light to form the scan line image. The spatial light modulators include light modulating elements that are arranged in two-dimensional array and are individually adjustable to either pass/reflect received homogenous light portions to the anamorphic optical systems, or to block/redirect the homogenous light portions, thereby generating two-dimensional modulated light fields. Anamorphic optical systems are used to image and focus received modulated light field onto an associated substantially one-dimensional scan line portion on the scan structure. An image stitching controller modifies the image data sent to each spatial light modulator such that selected light modulating elements are enabled or disabled, thereby electronically stitching the scan line portions to form a seamlessly stitched scan line image.

FIELD OF THE INVENTION

This invention relates to imaging methods, and in particular tosingle-pass, high resolution imaging methods for high speed lithographicdata image generation.

BACKGROUND OF THE INVENTION

Laser imaging systems are extensively used to generate images inapplications such as mask and maskless lithographic patterning, lasertexturing of surfaces, and laser cutting machines. Laser printers oftenuse a raster optical scanner (ROS) that sweeps a laser perpendicular toa process direction by utilizing a polygon or galvo scanner, whereas forcutting applications lasers imaging systems use flatbed x-y vectorscanning.

One of the limitations of the laser ROS approach is that there aredesign tradeoffs between image resolution and the lateral extent of shescan line. These tradeoffs arising from optical performance limitationsat the extremes of the scan line such as image field curvature. Inpractice, it is extremely difficult to achieve 1200 dpi resolutionacross a 20″ imaging swash with single galvanometers or polygonscanners. Furthermore, a single laser head motorized x-y flatbedarchitecture, ideal for large area coverage, is too slow for most highspeed printing processes.

For this reason, monolithic light emitting diode (LED) arrays of up to20″ in width have an imaging advantage for large width xerography.Unfortunately, present LED array are only capable of offering 10milliWatt power levels per pixel and are therefore only useful for somenon-thermal imaging applications such as xerography. In addition, LEDbars have differential aging and performance spread. If a single LEDfails it requires the entire LED bar be replaced. Many other imaging ormarking applications require much higher power. For example, lasertexturing, or cutting applications can require power levels in the 10W-100 W range. Thus LED bars cannot be used for these high powerapplications. Also, it is difficult to extend LEDs to higher speeds orresolutions above 1200 dci without using two or more rows of staggeredheads.

Higher power semiconductor laser arrays in the range of 100 mW-100 Wattsdo exist. Most often they exist in a 1D array format such as on a laserdiode bar often about 1 cm in total width. Another type of high powerdirected light source are 2D surface emitting VCSEL arrays. However,neither of these high power laser technologies allow for the laser pitchbetween nearest neighbors to be compatible with 600 dpi or higherimaging resolution. In addition, neither of these technologies allow forthe individual high speed control of each laser. Thus high powerapplications such as high power overhead projection imaging systems,often use a high power source such as a laser in combination with aspatial light modulator such as a DLP™ chip from Texas Instruments orliquid crystal arrays.

Prior art has shown that if imaging systems are arrayed side by side,they can be used to form projected images that overlap wherein theoverlap can form a larger image using software to stitch together theimage patterns into a seamless pattern. This has been shown in manymaskless lithography systems such as those for PC board manufacturing aswell as for display systems. In the past such arrayed imaging systemsfor high resolution applications have been arranged in such a way thatthey must use either two rows of imaging subsystems or use a double passscanning configuration in order to stitch together a continuous highresolution image. This is because of physical hardware constraints onthe dimensions of the optical subsystems. The double imaging rowconfiguration can still be seamlessly stitched together using a conveyorto move the substrate in single direction but such a system requires alarge amount of overhead hardware real estate and precision alignmentbetween each imaging row.

For the maskless lithography application, the time between exposure anddevelopment of photoresist to be imaged is not critical and thereforethe imaging of the photoresist along a single line does not need beexposed at once. However, sometimes the time between exposure anddevelopment is critical. For example, xerographic laser printing isbased on imaging a photoreceptor by erasing charge which naturallydecays over time. Thus the time between exposure and development is nottime invariant. In such situations, it is desirable for the exposuresystem to expose a single line, or a few tightly spaced adjacent linesof high resolution of a surface at once.

In addition to xerographic printing applications, there are othermarking systems were the time between exposure and development arecritical. One example is the laser based variable data lithographicmarking approach originally disclosed by Carley in U.S. Pat. No.3,800,699 entitled, “FOUNTAIN SOLUTION IMAGE APPARATUS FOR ELECTRONICLITHOGRAPHY”. In standard offset lithographic printing, a static imagingplate is created that has hydrophobic imaging and hydrophilicnon-imaging regions. A thin layer of water based dampening solutionselectively wets the plate and forms an oleophobic layer whichselectively rejects oil-based inks. In variable data lithographicmarking disclosed in U.S. Pat. No. 3,800,699, a laser can be used topattern ablate the fountain solution to form variable imaging regions onthe fly. For such a system, a thin layer of dampening solution alsodecays in thickness over time, due to natural partial pressureevaporation into the surrounding air. Thus it is also advantageous toform a single continuous high power laser imaging line pattern formed ina single imaging pass step so that the liquid dampening film thicknessis the same thickness everywhere at the image forming laser ablationstep. However, for most arrayed high power high resolution imagingsystems, the hardware and packaging surrounding a spatial lightmodulator usually prevent a seamless continuous line pattern to beimaged. Furthermore, for many areas of laser imaging such as texturing,lithography, computer to plate making, large area die cutting, orthermal based printing or other novel printing applications, what isneeded is laser based imaging approach with high total optical powerwell above the level of 1 Watt that is scalable across large processwidths in excess of 20″ as well as having achievable resolution greaterthan 1200 dpi and allows high resolution high speed imaging in a singlepass.

SUMMARY OF THE INVENTION

The present invention is directed to a method for generating asubstantially one-dimensional scan line image in response to receivedimage data by separating the image data into two or more portions, andcontrolling first and second groups of modulating elements disposed intwo-dimensional (2D) arrays using the respective image data portions togenerate two-dimensional modulated light fields that are thenanamorphically imaged/concentrated and stitched together to form theform the scan line image. In one embodiment, the method utilizes animaging (e.g., lithographic) apparatus including two or more spatiallight modulators that include the groups of modulating elements, andassociated anamorphic optical systems that anamorphically image themodulated light in the process and cross-process directions andconcentrate (converged or linearly-focused) the modulated light in asubstantially one-dimensional imaging region on a targeted scanstructure (e.g., a drum roller). Each spatial light modulator (e.g.,digital micromirror (DMD) devices, electro-optic diffractive modulatorarrays, or arrays of thermo-optic absorber elements) includesindividually addressable elements having light modulating structuresthat modulate (e.g., either passes or impedes/redirects) associatedportions of the homogenous light according to predetermined image data.Each anamorphic optical system images and concentrates the modulatedhomogenous light received from an associated spatial light modulator toform an associated scan line portion, and the scan line portions formedby each anamorphic optical system collectively form the elongated scanline in the imaging region of the scan structure. Here the termanamorphic optical system refers to any system of optical lens, mirrors,or other elements that project the light from an object plane such as apattern of light formed by a spatial light modulator, to a final imagingplane with a differing amount of magnification along orthogonaldirections. Thus, for example, a square-shaped imaging pattern formed bya 2D spatial light modulator could be anamorphically projected so as tomagnify its width and at same time demagnify (or bring to a concentratedfocus) its height thereby transforming square shape into an image of anextremely thin elongated rectangular shape at the final image plane. Byutilizing the anamorphic optical system to concentrate the modulatedhomogenous light, high total optical intensity (flux density) (i.e., onthe order of hundreds of Watts/cm²) can be generated on any point of thescan line image without requiring a high intensity light source passthrough a spatial light modulator, thereby facilitating a reliable yethigh power imaging system that can be used, for example, for single-passhigh resolution high speed printing applications. Furthermore, it shouldbe clarified that the homogenous light generator, may include multipleoptical elements such as light pipes or lens arrays, that reshape thelight from one or more non-uniform sources of light so as to providesubstantially uniform light intensity across at least one dimension of atwo-dimensional light field. Many existing technologies for generatinglaser “flat top” profiles with a high degree of homogenization exist inthe field.

According to an aspect of the present invention, each spatial lightmodulator includes multiple light modulating elements that are arrangedin a two-dimensional array, and a controller (e.g., an SRAM array) thatindividually controls the modulating elements such that the lightmodulating structure of each modulating element is adjustable between an“on” (first) modulated state and an “off” (second) modulated stateaccording to received image data. When one of the modulating elements isin the “on” modulated state, its light modulating structure directs thereceived light portion in a corresponding predetermined direction (i.e.,the element passes the associated light portion toward the anamorphicoptical system). Conversely, when the modulating element is in the “off”modulated state, the associated received light portion is prevented frompassing along the corresponding predetermined direction by themodulating element to the anamorphic optical system. By modulatinghomogenous light in this manner prior to being anamorphically imaged andconcentrated, the present invention is able to produce a high power scanline along the entire imaging region simultaneously, as compared with arastering system that only applies high power to one point of the scanline at any given instant. In addition, because the relatively low powerhomogenous light is spread over the large number of modulating elements,the present invention can be produced using low-cost, commerciallyavailable spatial light modulating devices, such as digital micromirror(DMD) devices, electro-optic diffractive modulator arrays, or arrays ofthermo-optic absorber elements.

According to an embodiment of the present invention, each spatial lightmodulator includes light modulating elements that are arranged in anarray of rows and columns, and the associated anamorphic optical systemis arranged to converge light portions received from each column into anassociated imaging region (“pixel”) of the resulting scan line portion.That is, the light portions from all of the light modulating elements ina given column are imaged and concentrated by the anamorphic opticalsystem onto the same corresponding imaging region of the scan lineportion so that the resulting imaging “pixel” produced on the imagingregion is the composite light from all light modulating elements in thegiven column that are in the “on” state. A key aspect of the presentinvention lies in understanding that the light portions passed by eachlight modulating element represent one bit of binary image data that aredelivered to the imaging region of the scan structure by an associatedanamorphic optical systems, so that the brightness of each imagingregion “pixel” is controlled by the number of elements in the associatedcolumn that are in the “on” state. Accordingly, by individuallycontrolling the multiple modulating elements disposed in each column,and by converging the light passed by each column onto a correspondingimaging region, the present invention provides an imaging system havinggray-scale capabilities using constant (non-modulated) homogenous light.In addition, if the position of a group of “on” pixels in each column isadjusted up or down the column, this arrangement facilitates softwareelectronic compensation of bow (i.e. “smile” of a straight line) andskew.

According to an aspect of the invention, the method further utilizes animage stitching controller that serves to electronically stitch theanamorphically imaged and concentrated light fields such that the scanline image is seamlessly produced in the imaging region of the targetedscan structure. In one embodiment, the electronic stitching involvesseparating the “raw” image data representing an entire scan line intogroups of modified image data that are respectively transmitted to eachspatial light modulators such that the resulting scan line portions forma seamless scan line image in the imaging region of the scan structure.In one embodiment, the associated spatial light modulators andanamorphic optical systems are purposefully arranged such that theanamorphically imaged and concentrated light fields produced by adjacentanamorphic optical systems are overlapped in the imaging region of thescan structure. That is, adjacent spatial light modulators andanamorphic optical systems are arranged such that the outmost edges ofthe anamorphically imaged and concentrated light fields generate scanline portions in the same overlap region of the imaging region. Thisoverlap ensures that the imaging apparatus is able to produce the scanline without gaps that can be caused when the adjacent spatial lightmodulators are placed too far apart during assembly, and iselectronically corrected (i.e., the potential overlap is eliminated) bymodifying the image data such that selected columns of light modulatingelements of one or more of the spatial light modulators are effectively“disabled” (i.e., image data is not sent the this column, and itselements remain in the “off” modulated state). By selectively disablingoverlapping columns of light modulating elements, the resultingconcentrated scan line portions are stitched together to form a seamlesselongated scan line image. Similarly, vertical (cross-scan) offsetsbetween adjacent spatial light modulators, which can also occur duringassembly, are corrected by modifying image data transmitted to one ofthe light modulating elements is shifted to a different row ofmodulating elements such that a feature extending parallel to the scanline image is aligned in a cross-scan direction (e.g., vertical) withinthe elongated imaging region. By utilizing the modulation controller toselectively deactivate modulating elements of adjacent spatial lightmodulators that project image “pixels” into each overlap region, thepresent invention provides an imaging apparatus in which image alignmentimperfections are corrected utilizing relatively straight-forward“software” control techniques, thereby easing manufacturing tolerancesand facilitating the production of low-cost, high resolutionlithographic apparatus that are scalable to any scan line length.

According to an embodiment of the present invention, each homogenouslight generator includes one or more light sources and a lighthomogenizer optical system for homogenizing light beams generated by thelight sources. High power laser light homogenizers are commerciallyavailable from several companies including Lissotschenko Microoptik alsoknown as LIMO GmbH located in Dortmund, Germany. One benefit ofconverting a point source high intensity light beams (i.e., light beamshaving a first, relatively high flux density) to relatively lowintensity homogenous light source (i.e., light having a second fluxdensity that is lower than the flux density of the high energy beam) inthis manner is that this arrangement facilitates the use of a highenergy light source (e.g., a laser or light emitting diode) withoutrequiring the construction of spatial light modulator using specialoptical classes and antireflective coatings that can handle the highenergy light. That is, by utilizing a homogenizer to spread the highenergy laser light out over an extended two-dimensional area, theintensity (Watts/cc) of the light over a given area (e.g., over the areaof each modulating element) is reduced to an acceptable level such thatlow cost optical glasses and antireflective coatings can be utilized toform spatial light modulator with improved power handling capabilities.Spreading the light uniformly out also eliminates the negatives imagingeffects that point defects (e.g., microscopic dust particles orscratches) have on total light transmission losses.

According to another embodiment of the present invention, the methodutilizes an anamorphic optical system including a cross-process opticalsubsystem and a process-direction optical subsystem that concentrate themodulated light portions received from the spatial light modulator suchthat the concentrated modulated light forms the substantiallyone-dimensional scan line image, wherein the concentrated modulatedlight at the scan line image has a higher optical intensity (i.e., ahigher flux density) than that of the homogenized light. Byanamorphically concentrating (focusing) the two-dimensional modulatedlight pattern to form a high energy elongated scan line, the imagingsystem of the present invention outputs a higher intensity scan line.The scan line is usually directed towards and swept over a movingimagine surface near its focus. This allows an imaging system to beformed such as a printer. The direction of the surface sweep is usuallyperpendicular to the direction of the scan line and is customarilycalled the process direction. In addition, the direction parallel to thescan line is customarily called the cross-process direction. The scanline image formed may have different pairs of cylindrical oracylindrical lens that address the converging and tight focusing of thescan line image along the process direction and the projection andmagnification of the scan line image along the cross-process direction.In one specific embodiment, the cross-process optical subsystem includesfirst and second cylindrical or acylindrical lenses arranged to projectand magnify the modulated light onto the elongated scan line in across-process direction, and the process-direction optical subsystemincludes a third cylindrical or acylindrical focusing lens arranged toconcentrate and demagnify the modulated light on the scan line in adirection parallel to a process direction. This arrangement facilitatesgenerating a wide scan line that can be combined (“stitched” or blendedtogether with a region of overlap) with adjacent optical systems toproduce an assembly having a substantially unlimited length scan line.An optional collimating field lens may also be disposed between thespatial light modulator and cylindrical or acylindrical focusing lens inboth the process and cross-process direction. It should be understoodthat the overall optical system may have several more elements to helpcompensate for optical aberrations or distortions and that such opticalelements may be transmissive lenses or reflective mirror lenses withmultiple folding of the beam path.

According to a specific embodiment of the present invention, the methoduses a spatial light modulator comprising a DLP™ chip from TexasInstruments, referred to as a Digital Light Processor in the packagedform. The semiconductor chip itself is often referred to as a DigitalMicromirror Device or DMD. This DMD includes an two dimensional array ofmicroelectromechanical (MEMs) mirror mechanisms disposed on a substrate,where each MEMs mirror mechanism includes a mirror that is movablysupported between first and second tilted positions according toassociated control signals generated by a controller. The spatial lightmodulator and the anamorphic optical system are positioned in a foldedarrangement such that, when each mirror is in the first tilted position,the mirror reflects its associated received light portion toward theanamorphic optical system, and when the mirror is in the second tiltedposition, the mirror reflects the associated received light portion awayfrom the anamorphic optical system towards a beam dump. An optional heatsink is fixedly positioned relative to the spatial light modulator toreceive light portions from mirrors disposed in the second tiltedposition towards the beam dump. An optional frame is utilized tomaintain each of the components in fixed relative position. An advantageof a reflective DMD-based imaging system is that the folded optical patharrangement facilitates a compact system footprint.

According to yet another embodiment of the present invention, the methodincludes tilting the spatial light modulators relative to theirrespective anamorphic optical systems such that the rows of modulatingelements are aligned at an acute tilt angle relative to the scan lineimage, whereby each anamorphic optical system focuses each modulatedlight portion onto an associated sub-imaging region of elongated scanline image. The benefit of this tilted orientation is that the apparatusproduces a higher resolution linear image than that possible using aright-angle orientation, and allows for sub-pixel spacingaddressability, and provides an opportunity to utilize software tofurther align image “pixels” spanning adjacent scan image portions withfractional precision in both the X-axis and Y-axis directions. Thespatial light modulators are optionally set at a tilt angle thatproduces an alignment of each imaging region with multiple elementsdisposed in different columns of the array, thereby facilitatingvariable resolution and variable intensity. This arrangement alsofacilitates software adjustment for manufacturing defects such as bow,tilt and process direction velocity imperfections such as banding.

According to another specific embodiment of the present invention, themethod is performed using an assembly includes multiple imaging systems,where each imaging systems includes means for generating homogenouslight such that the homogenous light forms a substantially uniformtwo-dimensional homogenous light field, means for modulating portions ofthe homogenous light in accordance with the predetermined scan lineimage data such that the modulated light portions form a two-dimensionalmodulated light field, and means for anamorphically concentrating themodulated light portions along the process direction and anamorphicallyprojecting with magnification the light field along the cross-processdirection such that the concentrated modulated light portions form anelongated scan line image. Under this arrangement, multiple imagingsystems can be situated side by side to form a substantially collinear“macro” single long scan line image scalable to lengths well over twentyinches. This arrangement allows for the entire system to sweep avariable optical pattern over an imaging substrate in a single passwithout any staggering or time delays during the sweep between eachimaging system subunit. In a specific embodiment, the spatial lightmodulator of each system is a DMD device, and the anamorphic opticalsystem is positioned in the folded arrangement described above. Anotheradvantage of the DMD-based imaging system is that the folded arrangementfacilitates combining multiple imaging systems to produce a scan line inexcess of 20″ using presently available DMD devices. It should also beunderstood that each scan-line that is stitched together need not bedirected exactly normal to the same focal plane imaging surface, i.e.the optical paths need not be collinear between adjacent subsystems. Infact in order to facilitate more room for the body of each individualoptical system, it is possible for the scan line to be received fromeach adjacent subsystem at small interlaced angles.

According to another embodiment of the present invention, the methodpositions a scanning/printing apparatus that includes the single-passimaging system described above such that the concentrated modulatedlight from the anamorphic optical system is directed onto a scanstructure (e.g., an imaging drum cylinder). According to a specificembodiment, the imaging surface may be one that holds a damping(fountain) solution such as is used for variable data lithographicprinting.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features, aspects and advantages of the presentinvention will become better understood with regard to the followingdescription, appended claims, and accompanying drawings, where:

FIG. 1 is a modified block diagram depicting a generalized imagingapparatus including two or more spatial light modulators according to anexemplary embodiment of the present invention;

FIG. 2 is a top side perspective view showing a portion of the apparatusof FIG. 1 according to an embodiment of the present invention;

FIGS. 3(A) and 3(B) are partial perspective views showing a method formodifying image data to adjust for image overlap in the apparatus ofFIG. 1 according to an embodiment of the present invention;

FIGS. 4(A) and 4(B) are partial perspective views showing a method forfurther modifying image data to adjust for vertical misalignment ofadjacent spatial light modulators of the apparatus of FIG. 1 accordingto a specific embodiment of the present invention;

FIGS. 5(A) and 5(B) are simplified top and side views, respectively,showing alternative homogenous light generators utilized by imagingapparatus of FIG. 1 according to alternative embodiments of the presentinvention;

FIGS. 6(A) and 6(B) are simplified top and side views, respectively,showing an anamorphic optical system utilized by imaging apparatus ofFIG. 1 according to a specific embodiment of the present invention;

FIG. 7 is a perspective view showing a portion of a DMD-type spatiallight modulator utilized by the apparatus of FIG. 1 according to aspecific embodiment of the present invention;

FIG. 8 is an exploded perspective view showing a light modulatingelement of the DMD-type spatial light modulator of FIG. 7 in additionaldetail;

FIGS. 9(A), 9(B) and 9(C) are perspective views showing the lightmodulating element of FIG. 8 during operation;

FIG. 10 is a simplified diagram showing a portion of an imagingapparatus including the DMD-type spatial light modulator of FIG. 7 in afolded arrangement according to a specific embodiment of the presentinvention;

FIG. 11 is an exploded perspective view showing a portion of anotherimaging apparatus utilizing the DMD-type spatial light modulator in thefolded arrangement according to another specific embodiment of thepresent invention;

FIG. 12 is a perspective view showing the imaging apparatus portion ofFIG. 11 in an assembled state;

FIG. 13 is a perspective view showing an imaging apparatus according toanother specific embodiment of the present invention;

FIG. 14 is a perspective view showing a portion of another imagingapparatus including a tilted spatial light modulator according toanother specific embodiment of the present invention;

FIG. 15 is a simplified diagram depicting the tilted spatial lightmodulator of FIG. 14 during operation;

FIG. 16 is a perspective view showing another imaging apparatus portionincluding a tilted DMD-type spatial light modulator according to anotherspecific embodiment of the present invention;

FIG. 17 is a simplified diagram depicting two tilted spatial lightmodulators of an imaging apparatus according to another specificembodiment of the present invention;

FIG. 18 is a simplified diagram depicting the two tilted spatial lightmodulators of FIG. 17 after image data is modified according to anembodiment of the present invention;

FIG. 19 is a perspective view showing an imaging apparatus according toanother specific embodiment of the present invention; and

FIGS. 20(A) and 20(B) are simplified perspective diagrams showingalternative imaging apparatus according to alternative specificembodiments of the present invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The present invention relates to improvements in imaging methods andrelated apparatus (e.g., scanners and printers). The followingdescription is presented to enable one of ordinary skill in the art tomake and use the invention as provided in the context of a particularapplication and its requirements. As used herein, directional terms suchas “upper”, “upwards”, “lower”, “downward”, “front”, “rear”, areintended to provide relative positions for purposes of description, andare not intended to designate an absolute frame of reference. Inaddition, the phrases “integrally connected” and “integrally molded” isused herein to describe the connective relationship between two portionsof a single molded or machined structure, and are distinguished from theterms “connected” or “coupled” (without the modifier “integrally”),which indicates two separate structures that are joined by way of, forexample, adhesive, fastener, clip, or movable joint. Variousmodifications to the preferred embodiment will be apparent to those withskill in the art, and the general principles defined herein may beapplied to other embodiments. Therefore, the present invention is notintended to be limited to the particular embodiments shown anddescribed, but is to be accorded the widest scope consistent with theprinciples and novel features herein disclosed.

FIG. 1 is a perspective view showing a single-pass imaging apparatus 200according to a simplified exemplary embodiment of the present invention,and FIG. 2 is a perspective view showing a portion of a single-passimaging apparatus 200 in additional detail.

Referring to FIG. 1, imaging apparatus 200 generally includes ahomogenous light generator 110, at least two spatial light modulators120-1 and 120-2, at least two anamorphic optical (e.g., projection lens)system 130-1 and 130-2, scan structure 160 upon which a scan line imageSL is generated in response to “raw” image data IDA, and an imagestitching controller 170 that serves to modify the received image dataIDA in accordance with predetermined stitching data SD, and to producemodified image data groups IDB-1 and IDB-2 that are respectivelytransmitted to spatial light modulators 120-1 and 120-2, whereby spatiallight modulators 120-1 and 120-2 are cooperatively controlled as setforth below such that a seamless scan line image SL is generated in anelongated imaging region 167 of scan structure 160. Although the presentinvention is described below with reference to two or three associatedpairs of spatial light modulators and anamorphic optical systems,imaging apparatus produced in accordance with the present invention mayinclude any number of such pairs utilizing the characteristics describedbelow. In addition, anamorphic optical systems 130-1 and 130-2 arerepresented for the purposes of simplification in FIG. 1 by singlegeneralized anamorphic projection lens. In practice anamorphic systems130-1 and 130-2 are typically each composed of multiple separatecylindrical or acylindrical lenses, such as described below withreference to FIGS. 6(A), 6(B) and 19.

Referring to the left side of FIG. 1 and to the lower left portion ofFIG. 2, homogenous light generator 110 serves to generate continuous(i.e., constant/non-modulated) homogenous light 118A that forms asubstantially uniform two-dimensional homogenous light field 119A. Thatis, homogenous light generator 110 is formed such that all portions ofhomogenous light field 119A, which is depicted by the projected dottedrectangular box (i.e., homogenous light field 119A does not form astructure), receive light energy having substantially the same constantenergy level (i.e., substantially the same flux density). Fordescriptive purposes, light that directed from homogenous lightgenerator 110 to spatial light modulator 120-1 is referred to homogenouslight portion 118A-1, and light that directed from homogenous lightgenerator 110 to spatial light modulator 120-2 is referred to homogenouslight portion 118A-2. As set forth in additional detail below,homogenous light generator 110 is implemented using any of severaltechnologies, and is therefore depicted in a generalized form in FIGS. 1and 2.

Referring to the center left portions of FIG. 1, spatial lightmodulators 120-1 and 120-2 are disposed in homogenous light field 119A,and serve the purpose of modulating portions of homogenous light 118Aaccordance with modified image data groups IDB-1 and IDB-2. As indicatedin FIG. 1, spatial light modulator 120-1 receives homogenous lightportion 118A-1 from homogeneous light generator 110, and selectivelypasses modulated light portion 118B-1 to anamorphic optical system130-1. Similarly, spatial light modulator 120-2 receives homogenouslight portion 118A-2 from homogeneous light generator 110, andselectively passes modulated light portion 118B-2 to anamorphic opticalsystem 130-2.

FIG. 2 shows a portion of apparatus 200 including exemplary spatiallight modulator 120-1 and a simplified associated anamorphic opticalsystem 130-1, along with an associated portion of homogeneous lightgenerator 110 and elongated imaging region 167 of scan structure 160. Itis understood that spatial light modulator 120-2 and anamorphic opticalsystem 130-2 are constructed and operate in a manner identical to thatdescribed with reference to FIG. 2. In a practical embodiment a suitablespatial light modulator can be purchased commercially and wouldtypically have two-dimensional (2D) array sizes of 1024×768 (SVGAresolution) or higher resolution with light modulation element (pixel)spacing on the order of 5-20 microns. For purposes of illustration, onlya small subset of light modulation elements is depicted in the figuresdiscussed herein.

Referring to the lower left-center portion of FIG. 2, spatial lightmodulator 120-1 generally includes a modulating element array 122 madeup of modulating elements 125-111 to 125-143 disposed on a supportstructure 124, and a device control circuit (controller) 126 fortransmitting image control signals 127 to modulating elements 125-11 to125-43 in response to modified image data IDB-1. Modulating elements125-111 to 125-143 are arranged in a two-dimensional array 122 anddisposed such that a light modulating structure (e.g., a mirror, adiffractive element, or a thermo-optic absorber element) of eachmodulating element 125-111 to 125-143 receives a corresponding portionof homogenous light 118A (e.g., modulating elements 125-111 and 125-122respectively receive homogenous light portions 118A-111 and 118A-122),and is positioned to selectively pass (modulate) the receivedcorresponding modulated light portion along a predetermined directiontoward anamorphic optic 130-1 (e.g., modulating element 125-122 passesmodulated light portion 118B-122 to anamorphic optical system 130-1, but125-111 blocks light from reaching anamorphic optical system 130-1). Inparticular, each light modulating element 125-111 to 125-143 isindividually controllable by controller 126 in response to associatedcontrol signals 127 to switch between an “on” (first) modulated stateand an “off” (second) modulated state. When a given modulating elementis in the “on” modulated state, the modulating element is actuated todirect the given modulating element's associated received light portiontoward anamorphic optic system 130-1. For example, in the simplifiedexample, modulating element 125-143 is unshaded (white) to indicate itis rendered transparent in response to the associated control signalsuch that light portion 118A-143 passes through modulating element125-143 toward anamorphic optic 130-1, whereby in the exemplaryembodiment the passed light portion becomes “modulated” light portion118B-143 that passes from modulating element 125-143 to a correspondingportion of anamorphic optic system 130-1. Conversely, when a givenmodulating element is in the “off” modulated state, the modulatingelement is actuated to prevent (e.g., block or redirect) the givenmodulating element's associated received light portion. For example,modulating element 125-111 is darkened to indicate it is opaque, therebypreventing received light portion 118A-111 from being passed toanamorphic optical system 130-1. By selectively turning “on” or “off”modulating elements 125-111 to 125-143 in accordance with modified imagedata IDB-1 supplied to controller 126 from image stitching controller170 (see FIG. 1), spatial light modulator 120-1 serves to modulate(i.e., pass or not pass) portions of continuous homogenous light 118A-1such that a two-dimensional modulated light field 119B-1 is generatedthat is passed to anamorphic optical system 130-1. As set forth inadditional detail below, spatial light modulator 120-1 is implementedusing any of several technologies, and is therefore not limited to thegeneralized “pass through” arrangement depicted in FIG. 2.

Referring to the center right portion of FIG. 2, anamorphic opticalsystem 130-1 serves to anamorphically image and concentrate (focus) themodulated light portions, which are received from spatial lightmodulator 120-1 by way of two-dimensional light field 119B-1, onto anassociated portion of imaging region 167 such that elongated scan lineportion SL-1 is generated having a width S1 (i.e., measured in theX-axis direction indicated in FIG. 2). In particular, anamorphic opticalsystem 130-1 includes one or more optical elements (e.g., lenses ormirrors) that are positioned to receive the two-dimensional pattern oflight field 119B-1 that are directed to anamorphic optical system 130-1from spatial light modulator 120-1 (e.g., modulated light portion118B-143 that is passed from modulating element 125-143), where the oneor more optical elements (e.g., lenses or mirrors) are arranged to imageand concentrate the received light portions to a greater degree alongthe cross-scan (e.g., Y-axis) direction than along the scan (X-axis)direction, whereby the received light portions are anamorphicallyfocused to form an elongated scan line image portion SL-1 that extendsparallel to the scan (X-axis) direction. As set forth in additionaldetail below, anamorphic optical systems 130-1 and 130-2 are implementedusing any of several optical arrangements, and is therefore not limitedto the generalized lens depicted in FIGS. 1 and 2.

According to an aspect of the present invention, light modulatingelements 125-111 to 125-143 of spatial light modulator 120-1 aredisposed in a two-dimensional array 122 of rows and columns, andanamorphic optical system 130-1 is arranged to concentrate lightportions passed through each column of modulating elements on to eachimaging region SL-11 to SL-14 of scan line image portion SL-1. As usedherein, each “column” includes light modulating elements arranged in adirection that is substantially perpendicular to scan line image portionSL-1 (e.g., light modulating elements 125-111, 125-112 and 125-113 aredisposed in the rightmost column of array 122), and each “row” includeslight modulating elements arranged in a direction substantially parallelto scan line image portion SL-1 (e.g., light modulating elements125-111, 125-121, 125-131 and 125-141 are disposed in the uppermost rowof array 122). In the simplified arrangement shown in FIG. 2, any lightpassed through elements 125-111, 125-112 and 125-113 is imaged andconcentrated by anamorphic optical system 130-1 onto imaging regionSL-11, any light passed through elements 125-121, 125-122 and 125-123 isconcentrated onto imaging region SL-12, any light passed throughelements 125-131, 125-132 and 125-133 is concentrated onto imagingregion SL-13, and any light passed through elements 125-141, 125-142 and125-143 is concentrated onto imaging region SL-14.

According to another aspect of the present invention, grayscale imagingis achieved by controlling the on/off states of selected modulatingelements in each column of array 122. That is, the brightness (ordarkness) of the “spot” formed on each imaging region SL-11 to SL-14 iscontrolled by the number of light modulating elements that are turned“on” in each associated column. For example, referring to the imagingregions located in the upper right portion of FIG. 2, all of lightmodulating elements 125-111, 125-112 and 125-113 disposed in theleftmost column of array 122 are turned “off”, whereby image regionSL-11 includes a “black” spot, as depicted in the upper right portion ofFIG. 2. In contrast, all of light modulating elements 125-141, 125-142and 125-143 disposed in the rightmost column of array 122 are turned“on”, whereby light portions 118B-141, 118B-142 and 118B-143 pass fromspatial light modulator 120-1 and are concentrated by anamorphic opticalsystem 130-1 such that imaging region SL-14 includes a maximumbrightness (“white”) spot. The two central columns are controlled toillustrate gray scale imaging, with modulating elements 125-121 and125-123 turned “off” and modulating element 125-122 turned “on” to passa single light portion 118B-123 that forms a “dark gray” spot on imagingregion SL-12, and modulating elements 125-131 and 125-133 turned “on”with modulating element 125-132 turned “off” to pass two modulated lightportions 118B-131 and 118B-133 that form a “light gray” spot on imagingregion SL-13. One key to this invention lies in understanding the lightportions passed by each light modulating element represent one pixel ofbinary data that is delivered to the scan line by anamorphic opticalsystem 130-1, so that brightness of each imaging pixel of the scan lineis determined by the number of light portions (binary data bits) thatare directed onto the corresponding imaging region. Modulated lightportions directed from each row (e.g., elements 125-111 to 125-141) aresummed with light portions directed from the other rows such that thesummed light portions are wholly or partially overlapped to produce aseries of composite energy profiles at imaging regions (scan line imagesegments) SL-11 to SL-14. Accordingly, by individually controlling themultiple modulating elements disposed in each column of array 122, andby concentrating the light passed by each column onto a single imageregion, the present invention provides an imaging system havinggray-scale capabilities that utilizes the constant (non-modulated)homogenous light 118A-1 generated by homogenous light generator 110.

Note that the simplified spatial light modulator 120-1 shown in FIGS. 1and 2 includes only three modulating elements in each column fordescriptive purposes, and those skilled in the art will recognize thatincreasing the number of modulating elements disposed in each column ofarray 122 would enhance gray scale control by facilitating theproduction of spots exhibiting additional shades of gray. In onepreferred embodiment at least 24 pixels are used in one column to adjustgrayscale, thus allowing for single power adjustments in scan linesegments of at close to 4%. A large number of modulating elements ineach column of array 122 also facilitates the simultaneous generation oftwo or more scan lines within a narrow swath, and also allows forscrolling of image data to prevent blurring as set forth in additionaldetail below. Yet another benefit to providing a large number of lightmodulating elements in each column is that this arrangement would allowsfor one or more “reserve” or “redundant” elements that are onlyactivated when one or more of the regularly used elements malfunctions,thereby extending the operating life of the imaging system or allowingfor corrections to optical line distortions such as bow (also known asline smile).

Referring again to FIG. 1, image stitching controller 170 modifies “raw”image data IDA in accordance with predetermined stitching data SD suchthat, when modified image data group IDB-1 is transmitted to spatiallight modulator 120-1 and modified image data group IDB-2 is transmittedto spatial light modulator 120-2, their respective light modulatingelements are cooperatively controlled such that the scan line portionsSL-1 and SL-2 seamlessly form scan line image SL in elongated imagingregion 167. Image data IDA consists of a series of electronic bitstransmitted to modulation controller 170 in order to generate scan lineimage SL, which is a one-dimensional line (or a few lines) of atwo-dimensional image or pattern. Similar to the type of image data thatis provided to a typical ROS-type image scanner or printer, image dataIDA includes groups of electronic bits (or bytes) that correspond todesired image pixels, where each image pixel is a dark, bright, gray,colored or otherwise characterized “spot” of a correspondingtwo-dimensional image or pattern. Image stitching controller 170utilizes stitching data SD to separates and modifies “raw” image dataIDA into two image data groups IDB-1 and IDB-2 such that, when modifiedimage data groups IDB-1 and IDB-2 are transmitted to spatial lightmodulators 120-1 and 120-2, they modulate homogenous light 118A suchthat scan line portions SL-1 and SL-2 collectively form scan line imageSL without gaps or overlaps. Note that image data IDA is supplied froman external source (e.g., a personal computer, not shown) according to apredetermined format. Those skilled in the art understand that variousformats may be utilized, and that the appended claims are not limited toany particular format.

Referring again to FIG. 1, according to an aspect of the presentinvention, at least one of spatial light modulators 120-1 and 120-2 andcorresponding anamorphic optical systems 130-1 and 130-2 arepurposefully arranged to produce an overlapping pattern in imagingregion 167 of scan structure 160. That is, the components are arrangedsuch that, if all of the modulating elements in spatial light modulators120-1 and 120-2 were turned “on”, the resulting scan line portions SL-1and SL-2 would overlap in region W. In particular, with all modulatingelements of adjacent spatial light modulators 120-1 and 120-2 turned“on”, the lowermost edge of anamorphically imaged and concentrated lightfield 119C-1 overlaps the uppermost end of anamorphically imaged andconcentrated light field 119C-2, whereby sections of scan line portionsSL-1 and SL-2 are simultaneously generated in overlap region W ofimaging region 167. This overlapping component arrangement ensures thatimaging apparatus 200 is able to produce the scan line SL without gapsthat can be caused when the adjacent anamorphic optical systems 130-1and 130-2 are placed too far apart during assembly.

According to another aspect of the present invention, image stitchingcontroller 170 serves to electronically correct the above-mentionedintentional overlap condition (and to make additional corrections, ifnecessary) utilizing predetermined stitching data SD, which is generatedafter assembly of apparatus 200 by determining the extend of anyoverlap/misalignment, and modifying the associated image data using themethods described below to correct the overlap/misalignment.

According to an embodiment of the present invention, in order to correctthe intentional horizontal (scan-wise) overlap condition describedabove, modified image data groups IBD-1 and IBD-2 are generated suchthat one or more columns of modulating elements of one or more ofspatial light modulators 120-1 and 120-2 are effectively “disabled”(i.e., image data is not sent the these columns, and its modulatingelements remain in the “off” modulated state) such that adjacent endportions of scan line portions SL-1 and SL-2 are aligned in the scandirection to produce a seamlessly stitched portion of scan line imageSL. This modification is illustrated with reference to the simplifiedexample shown in FIG. 3(A) and FIG. 3(B), which shows a portion ofapparatus 200 including portions of spatial light modulators 120-1 and120-2 and associated anamorphic optical systems 130-1 and 130-2. FIG.3(A) illustrates an attempt to generate a scan line image having twohorizontally arranged white “pixels”, and involves transmitting imagedata to spatial light modulators 120-1 and 120-2 such that adjacentelements on the two modulators (i.e., element 125-142 of spatial lightmodulator 120-1 and element 125-212 of spatial light modulator 120-2)are in the “on” modulated state. As described above, this modulationpattern produces modulated light portion 118B-142 of homogenous light118A to pass onto anamorphic optical system 130-1, and for modulatedlight portion 118B-212 to pass onto anamorphic optical system 130-2. Inthis example, due to the intentional overlapping arrangement,concentrated light portions 118B-132 and 118B-142 are respectivelydirected onto the same portion of imaging region 167 (which is shown inan enlarged fashion in FIG. 3(A) for illustrative purposes), therebyproducing a single white “dot” formed by scan line portion SL-14 of scanline image SL-1 and scan line portion SL-21 of scan line image SL-2. Asillustrated in FIG. 3(B), this overlap is addressed by electronicallydisabling the first rightmost column of spatial light modulator 120-2,and modifying the image data such that all image control data is shiftedto one column to the left (i.e., such that the associated image datacauses element 125-222 to turn “on” instead of element 125-212). Due tothe additional spacing between modulated light portions 118B-142 and118B-222, which are respectively passed by element 125-142 of spatiallight modulator 120-1 and element 125-222 of spatial light modulator120-2 and imaged and concentrated by anamorphic optical systems 130-1and 130-2 in the manner described above, two horizontally arranged white“dots” are formed by scan line portion SL-14 of scan line image SL-1 andscan line portion SL-22 of scan line image SL-2. By selectivelydisabling the overlapping columns of light modulating elements, theresulting concentrated scan line portions SL-1 and SL-2 are stitchedtogether to form a seamless elongated scan line image SL. In addition,once the necessary offset is determined, stitching data SD used by imagestitching controller 170 is updated to indicate that all image datatransmitted to spatial light modulator 120-2 is shifted one column tothe left, thereby effectively eliminating the overlapping pattern forall subsequent print/scan operations. Of course, the same stitchingresult could have been achieved by modifying stitching data SD to shiftimage data sent to spatial light modulator 120-1 to the right.

Referring to FIG. 4(A), according to an embodiment of the presentinvention, scan structure 160 is positioned such that imaging region 167is displaced from the X-axis focal point of anamorphic optical system130-1, whereby the cross-scan (Y-axis) position of scan line regions canbe altered depending on which modulating elements in each column are inthe “on” modulated state. In the example shown in FIG. 4(A), element125-142 is located in a central position of its associated column, sothe “white” portion of scan image region SL-12 is located in a centralregion of imaging region portion 167-12. Because element 125-141 islocated in the upper position of its associated column, the “white”portion of scan image region SL-14 would be shifted downward in imageregion portion 167-12 if element 125-141 where on instead of element125-142. Similarly, because element 125-143 is located in the lowermostposition of its associated column, the “white” portion of scan imageregion SL-14 would be located in a upper portion of imaging regionportion 167-12 if element 125-143 where on instead of element 125-142.According to another embodiment of the present invention, vertical(cross-scan) offsets between “pixels” generated by adjacent spatiallight modulators 120-1 and 120-2, which can also occur during assembly,are corrected by modifying the image data group transmitted to one ofspatial light modulators 120-1 or 120-2 such that the associated activemodulating element data is shifted to a different row of modulatingelements, whereby a feature of scan line image SL extending across scanline portions SL-1 and SL-2 is aligned in a cross-scan direction withinelongated imaging region 167. This modification is illustrated withreference to the simplified example shown in FIG. 4(A) and FIG. 4(B),which shows the same portion of apparatus 200 described above withreference to FIGS. 3(A) and 3(B), and assumes the horizontal adjustmenthas already been addressed. That is, modulated light portions 118B-142and 118B-222, which are respectively passed by element 125-142 ofspatial light modulator 120-1 and element 125-222 of spatial lightmodulator 120-2 and concentrated by anamorphic optical systems 130-1 and130-2 in the manner described above, produce two horizontally arrangedwhite “dots” that are formed by scan line region SL-14 and scan lineregion SL-22. However, as shown in FIG. 4(A), the two horizontallyarranged white “dots” are misaligned in the vertical (Y-axis) directionby an amount Y1 due to a slight misalignment during the assemblyprocess. As illustrated in FIG. 4(B), this misalignment is addressed byelectronically shifting the image data sent to spatial light modulator120-2 downward, (i.e., such that the associated image data causeselement 125-223 to turn “on” instead of element 125-222). Due to therealignment between modulated light portions 118B-142 and 118B-223,which are respectively passed by element 125-142 of spatial lightmodulator 120-1 and element 125-223 of spatial light modulator 120-2 andimaged and concentrated by anamorphic optical systems 130-1 and 130-2 inthe manner described above, two vertically aligned white “dots” areformed in scan line region SL-14 and scan line region SL-22. Byselectively shifting image data transferred to the spatial lightmodulators in this way, the resulting scan line portions SL-1 and SL-2are stitched together and aligned in the cross-scan (Y-axis) directionto form a seamless elongated scan line image SL. In addition, once thenecessary adjustment is determined, stitching data SD used by imagestitching controller 170 (see FIG. 1) is updated to indicate that allimage data transmitted to spatial light modulator 120-2 is shifted tothe right one column and shifted upward one row, thereby effectivelyeliminating the horizontal/vertical overlap/displacement for allsubsequent print/scan operations. Various components of apparatus 200that are generally described above will now be described in additionaldetail with reference to certain specific exemplary embodiments.

FIGS. 5(A) and 5(B) are simplified perspective views showing alternativehomogenous light generators 110B and 110C according to exemplaryspecific embodiments of the present invention. Referring to FIG. 5(A),homogenous light generator 110B includes a light source 112B includingone or more light generating elements (e.g., laser or light emittingdiodes) 115B fabricated or otherwise disposed on a suitable carrier(e.g., a semiconductor substrate) 111B, and a light homogenizing opticalsystem (homogenizer) 17B that produces homogenous light 118A byhomogenizing light beam 116B (i.e., mixing and spreading out light beam116B over an extended two-dimensional area). Those skilled in the artwill recognize that this arrangement effectively coverts theconcentrated, relatively high energy intensity of light beams 116Bgenerated by light generating elements 115B into dispersed, relativelylow energy flux homogenous light 118A that is substantially evenlydistributed onto modulating elements of the spatial light modulators.

One benefit of converting high energy beams 116B to relatively lowenergy homogenous light 118A in this manner is that this arrangementfacilitates the use of a high energy light source (e.g., a laser) togenerate beam 116B without requiring the construction of spatial lightmodulators 120-1 and 120-2 using special optical glasses andantireflective coatings that can handle the high energy light. That is,by utilizing homogenizer 117B to spread the high energy laser light outover an extended two-dimensional area, the intensity (Watts/cc) of thelight over a given area (e.g., over the area of each modulating element125-111 to 125-143, see FIG. 2) is reduced to an acceptable level suchthat low cost optical glasses and antireflective coatings can beutilized to form spatial light modulators 120-1 and 120-2. For example,when all of light modulating elements are turned “off”, each of lightmodulating elements is required to absorb or reflect a relatively smallportion of low energy homogenous light 118A. In contrast, in the absenceof homogenizer 117B, most of the energy of beams 116B would beconcentrated on one or a smaller number of elements, which would requirethe use of substantially more expensive optical glasses andantireflective coatings.

Another benefit of converting high energy beams 116B to relatively lowenergy homogenous light 118A is that this arrangement provides improvedpower handling capabilities. That is, if high energy laser beams 116Bwere passed directly to the spatial light modulators, then only one or asmall number of modulating elements could be used to control how muchenergy is passed to anamorphic optical systems 130-1/2 (e.g.,substantially all of the energy would be passed if the element wasturned “on”, or none would be passed if the element was turned “off”).By expanding high energy laser light 116B to provide low energyhomogenous light 118A over a wide area, the amount of light energypassed by the spatial light modulators to the anamorphic optical systemsis controlled with much higher precision.

According to alternative embodiments of the present invention, the lightsource utilized to generate the high energy beam can be composed asingle high power light generating element, or composed of multiple lowpower light generating elements that collectively produce the desiredlight energy. For high power homogenous light applications, the lightsource is preferably composed of multiple lower power light sources(e.g., edge emitting laser diodes or light emitting diodes) whose lightemissions are mixed together by the homogenizer optics and produce thedesired high power homogenous output. An additional benefit of usingseveral independent light sources is that laser speckle due to coherentinterference is reduced.

FIG. 5(A) illustrates a light source 112B according to a specificembodiment in which multiple edge emitting laser diodes 115B arearranged along a straight line that is disposed parallel to the rows oflight modulating elements (not shown). In alternative specificembodiments, light source 112B consists of an edge emitting laser diodebar or multiple diode bars stacked together. These sources do not needto be single mode and could consist of many multimode lasers.Optionally, a fast-axis collimation (FAC) microlens could be used tohelp collimate the output light from an edge emitting laser.

FIG. 5(B) illustrates a light source 112C according to another specificembodiment in which multiple vertical cavity surface emitting lasers(VCSELs) 115C are arranged in a two-dimensional array on a carrier 111C.This two-dimensional array of VCSELS could be stacked in any arrangementsuch as hexagonal closed packed configurations to maximize the amount ofpower per unit area. Ideally such laser sources would have high plugefficiencies (e.g., greater than 5) so that passive water cooling orforced air flow could be used to easily take away excess heat.

According to alternative embodiments of the present invention, lighthomogenizer 117B/C (which is shown in generalized form in FIGS. 5(A) and5(B)) is implemented using one or more tapered light pipes, a microlensarray, or any of several different additional technologies and methodsknown in the art.

FIGS. 6(A) and 6(B) are top and side views depicting a portion of animaging apparatus 200F including simplified anamorphic projection lenssystems 130F-1 and 130F-2 according to an exemplary specific embodimentof the present invention. In the embodiment shown in FIGS. 6(A) and6(B), each anamorphic projection lens system 130F-1 and 130F-2 includesan optional collimating optical subsystem 131F- and 131F-2, a two-lenscylindrical or acylindrical projection system 133F-1 and 133F2 formagnifying light in the cross process (scan) direction (i.e., along theX-axis), and a cylindrical or acylindrical focusing lens subsystem137F-1 and 137F-2 for focusing light in the process (cross-scan)direction (i.e., along the Y-axis). Note that focusing lens subsystem137F-1 and 137K-2 can be formed as a single lens or can be two separatelenses (as illustrated) using skills known in the art. As indicated bythe ray traces in FIGS. 6(A) and 6(B), optical subsystems 131F-1/2,133F-1/2 and 137F-1/2 are disposed in the optical path between spatiallight modulators 120F-1/2 and scan line SL, which is generated at theoutput of imaging system 200F. FIG. 6(A) is a top view indicating thatcollimating optical subsystem 131F-1/2 and cross-process opticalsubsystems 133F-1/2 act on the light portions passed by spatial lightmodulators 120-1/2 to direct the light along scan line image SL parallelto the X-axis (i.e., in the cross-process direction), and FIG. 6(B) is aside view that indicates how collimating optical subsystem 131F-1/2 andprocess-direction optical subsystems 137F-1/2 act on the light portionspassed by spatial light modulators 120-1/2 to focus the light on scanline image SL (i.e., perpendicular to the Y-axis, or process direction).

Collimating optical subsystems 131F-1 and 131F-2 respectively include acollimating field lens 132F-1 and 132F-2 formed in accordance with knowntechniques that is located immediately after spatial light modulators120F-1 and 120F-2 and is arranged to collimate the light portions thatare slightly diverging off of the surface of the spatial lightmodulators 120F-1 and 120F-2. Collimating optical subsystems 131F-1 and131F-2 are optional, and may be omitted when modulated light portions118B1 and 118B2 leaving spatial light modulator 120F-1 and 120F-2 arealready well collimated.

Each two-lens cylindrical or acylindrical projection system 133F-1 and133F-2 includes a first cylindrical or acylindrical lens 134F-1/2 and asecond cylindrical or acylindrical lens 136F-1/2 that are arranged toproject and magnify the light portions (imaging data) passed byassociated spatial light modulators 120F-1 and 120F-2 onto imagingsurface 167, which coincides with scan line SL. By producing a slightfanning out (spreading) of the light along the X-axis as indicated inFIG. 6(A), the scan line image produces the desired overlap W withoutmechanical interference between the adjacent optical subsystems. Theadvantage of this arrangement is that it allows the intensity of thelight (e.g., laser) power to be concentrated on scan line SL.

According to an embodiment of the invention, lens subsystems 137F-1/2share a third cylindrical or acylindrical lens 138F that concentratesthe projected imaging data down to a narrow high resolution line imageon imaging surface 167. Lens 138F must be high performance and have ahigh numerical aperture. Lenses 138F-1 and 138F-2 can be formed from assingle lenses or can be two lenses positioned side by side. The two lensversion will have to be positioned far enough from the image plane toavoid mechanical interference with the adjacent lens (or lenses). As thefocusing power of lenses 138F-1 and 138F-2 is increased, the intensityof the light on spatial light modulators 120F-1 and 120F-2 is reducedrelative to the intensity of scan line image SL at imaging surface 167.However, this means that cylindrical or acylindrical lenses 138F-1 and138F-2 must be placed closer to imaging surface 167 with a clearaperture extending to the very edges of lenses 138F-1 and 138F-2.Although single lenses 138F-1 and 138F-2 is indicated in the illustratedembodiment, two more separate lenses may be utilized to produce thedesired image concentration of lens subsystems 137F-12.

Referring to the right side of to FIG. 1, according to a specificembodiment of the present invention, apparatus 200 is a printer orscanner in which imaging drum cylinder 160 is coated with a fountainsolution that is evaporated on the imaging surface heated byanamorphically imaged and concentrated modulated light fields 119C-1 and119C-2, which are defined by the collection of anamorphically imaged andconcentrated modulated light portions 118C-1 and 118C-2 imaged andconcentrated by anamorphic optical systems 130-1 and 130-2,respectively. That is, instead of the selective application of ink by aplate and subsequent transfer of the ink to paper, as in standard offsetlithography, the ink is generally applied to a the imaging surface overa fountain solution that has been selectively evaporated on the platesurface heated by modulated light fields 119C-1 and 119C-2. In thisapparatus, only the dry (evaporated) areas of the imaging surface willhave ink transferred to it. The ink will subsequently be transferred topaper or other receiving media. Thus, variable data from evaporation istransferred, instead of constant data from the plate as in conventionalsystems. For this process to work using a rastered light source (i.e., alight source that is rastered back and forth across the scan line), asingle very high power light (e.g., laser) source would be required tosufficiently ablate the water solution in real time. The benefit of thepresent invention is that, because fountain solution liquid isevaporated from the entire scan line simultaneously, an offset pressconfiguration is provided at high speed using multiple relatively lowpower light sources.

According to alternative specific embodiments of the present invention,spatial light modulators 120-1 and 120-2 (see FIG. 1) are implementedusing commercially available devices including a digital micromirrordevice (DMD), such as a digital light processing (DLP®) chip availablefrom Texas Instruments of Dallas Tex., USA, an electro-optic diffractivemodulator array such as the Linear Array Liquid Crystal Modulatoravailable from Boulder Nonlinear Systems of Lafayette, Colo., USA, or anarray of thermo-optic absorber elements such as Vanadium dioxidereflective or absorbing mirror elements. Other spatial light modulatortechnologies may also be used. While any of a variety of spatial lightmodulators may be suitable for a particular application, manyprint/scanning applications today require a resolution 1200 dpi andabove, with high image contrast ratios over 10:1, small pixel size, andhigh speed line addressing over 30 kHz. Based on these specifications,the currently preferred spatial light modulator is the DLP™ chip due toits best overall performance.

FIG. 7 is a perspective view showing a portion of a DMD-type spatiallight modulator 120G that is utilized in accordance with a specificembodiment of the present invention, and includes a modulating elementarray 122G made up of multiple microelectromechanical (MEMs) mirrormechanisms 125G. Modulating element array 122G is consistent with DMDssold by Texas Instruments, wherein MEMs mirror mechanisms 125G arearranged in a rectangular array on a semiconductor substrate (i.e.,“chip” or support structure) 124G. Mirror mechanisms 125G are controlledas described below by a controller circuit 126G that also is fabricatedon substrate 124G according to known semiconductor processingtechniques, and is disposed below mirrors 125G. Although only sixty-fourmirror mechanisms 125G are shown in FIG. 7 for illustrative purposes,those skilled in the art will understand that any number of mirrormechanisms are disposed on DMD-type modulating element array 122G, andthat DMDs sold by Texas Instruments typically include several hundredthousand mirrors per device.

FIG. 8 is a combination exploded perspective view and simplified blockdiagram showing an exemplary mirror mechanism 125G-11 of DMD-typemodulating element array 122G (see FIG. 7) in additional detail. Fordescriptive purposes, mirror mechanism 125G-11 is segmented into anuppermost layer 210, a central region 220, and a lower region 230, allof which being disposed on a passivation layer (not shown) formed on anupper surface of substrate 124G. Uppermost layer 210 of mirror mechanism125G-11 includes a square or rectangular mirror (light modulatingstructure) 212 that is made out of aluminum and is typicallyapproximately 16 micrometers across. Central region 220 includes a yoke222 that connected by two compliant torsion hinges 224 to support plates225, and a pair of raised electrodes 227 and 228. Lower region 230includes first and second electrode plates 231 and 232, and a bias plate235. In addition, mirror mechanism 125G-11 is controlled by anassociated SRAM memory cell 240 (i.e., a bi-stable flip-flop) that isdisposed on substrate 124G and controlled to store either of two datastates by way of control signal 127G-1, which is generated by controller126G in accordance with image data as described in additional detailbelow. Memory cell 240 generates complementary output signals D andD-bar that are generated from the current stored state according toknown techniques.

Lower region 230 is formed by etching a plating layer or otherwiseforming metal pads on a passivation layer not shown) formed on an uppersurface of substrate 124G over memory cell 240. Note that electrodeplates 231 and 232 are respectively connected to receive either a biascontrol signal 127G-2 (which is selectively transmitted from controller126G in accordance with the operating scheme set forth below) orcomplementary data signals D and D-bar stored by memory cell 240 by wayof metal vias or other conductive structures that extend through thepassivation layer.

Central region 220 is disposed over lower region 230 using MEMStechnology, where yoke 222 is movably (pivotably) connected andsupported by support plates 225 by way of compliant torsion hinges 224,which twist as described below to facilitate tilting of yoke 222relative to substrate 124G. Support plates 225 are disposed above andelectrically connected to bias plate 235 by way of support posts 226(one shown) that are fixedly connected onto regions 236 of bias plate235. Electrode plates 227 and 228 are similarly disposed above andelectrically connected to electrode plates 231 and 232, respectively, byway of support posts 229 (one shown) that are fixedly connected ontoregions 233 of electrode plates 231 and 232. Finally, mirror 212 isfixedly connected to yoke 222 by a mirror post 214 that is attached ontoa central region 223 of yoke 222.

FIGS. 9(A) to 9(C) are perspective/block views showing mirror mechanism125G-11 of FIG. 7 during operation. FIG. 9(A) shows mirror mechanism125G-11 in a first (e.g., “on”) modulating state in which received lightportion 118A-G becomes reflected (modulated) light portion 118B-G1 thatleaves mirror 212 at a first angle θ1. To set the “on” modulating state,SRAM memory cell 240 stores a previously written data value such thatoutput signal D includes a high voltage (VDD) that is transmitted toelectrode plate 231 and raised electrode 227, and output signal D-barincludes a low voltage (ground) that is transmitted to electrode plate232 and raised electrode 228. These electrodes control the position ofthe mirror by electrostatic attraction. The electrode pair formed byelectrode plates 231 and 232 is positioned to act on yoke 222, and theelectrode pair formed by raised electrodes 227 and 228 is positioned toact on mirror 212. The majority of the time, equal bias charges areapplied to both sides of yoke 222 simultaneously (e.g., as indicated inFIG. 9(A), bias control signal 127G-2 is applied to both electrodeplates 227 and 228 and raised electrodes 231 and 232). Instead offlipping to a central position, as one might expect, this equal biasactually holds mirror 122 in its current “on” position because theattraction force between mirror 122 and raised electrode 231/electrodeplate 227 is greater (i.e., because that side is closer to theelectrodes) than the attraction force between mirror 122 and raisedelectrode 232/electrode plate 228.

To move mirror 212 from the “on” position to the “off” position, therequired image data bit is loaded into SRAN memory cell 240 by way ofcontrol signal 127G-1 (see the lower portion of FIG. 9(A). As indicatedin FIG. 9(A), once all the SRAM cells of array 122G have been loadedwith image data, the bias control signal is de-asserted, therebytransmitting the D signal from SRA cell 240 to electrode plate 231 andraised electrode 227, and the D-bar from SRAM cell 240 to electrodeplate 232 and raised electrode 228, thereby causing mirror 212 to moveinto the “off” position shown in FIG. 9(B), whereby received lightportion 118A-G becomes reflected light portion 118B-G2 that leavesmirror 212 at a second angle 72. In one embodiment, the flat uppersurface of mirror 212 tilts (angularly moves) in the range ofapproximately 10 to 12° between the “on” state illustrated in FIG. 9(A)and the “off” state illustrated in FIG. 9(B). When bias control signal127G-2 is subsequently restored, as indicated in FIG. 9(C), mirror 212is maintained in the “off” position, and the next required movement canbe loaded into memory cell 240. This bias system is used because itreduces the voltage levels required to address the mirrors such thatthey can be driven directly from the SRAM cells, and also because thebias voltage can be removed at the same time for the whole chip, soevery mirror moves at the same instant.

As indicated in FIGS. 9(A) to 9(C), the rotation torsional axis ofmirror mechanism 125G-11 causes mirrors 212 to rotate about a diagonalaxis relative to the x-y coordinates of the DLP chip housing. Thisdiagonal tilting requires that the incident light portions received fromthe spatial light modulator be projected onto each mirror mechanism 125Gat a compound incident angle so that the exit angle of the light isperpendicular to the surface of the DLP chip. This requirementcomplicates the side by side placement of DMD-type spatial lightmodulator 120G relative to the other components (e.g., the associatedanamorphic optical system) within an imaging apparatus.

FIG. 10 is a simplified perspective view showing a portion of an imagingapparatus 200G including a DMD-type spatial light modulator 120G-1,which is similar to spatial light modulator 120G described above withreference to FIGS. 7-9), where DMD-type spatial light modulator 120G-1is disposed in a preferred “folded” arrangement according to anotherembodiment of the present invention. Similar to the generalizedapparatus 200 discussed above with reference to FIG. 1, imagingapparatus 200G includes a homogenous light generator 110G and anassociated anamorphic optical system 130G-1 that function and operate asdescribed above. Imaging apparatus 200G is distinguished from thegeneralized system in that spatial light modulator 120G-1 is positionedrelative to homogenous light generator 110G and anamorphic opticalsystem 130G-1 at a compound angle such that incident homogenous light118A is neither parallel nor perpendicular to any of the orthogonal axesX, Y or Z defined by the surface of spatial light modulator 120G-1, andthe reflected light portions 118B-G1 and 118B-G2 (respectively producedwhen the mirrors are in the “on” and “off” positions as described above)are directed substantially normal or perpendicular to the surface ofspatial light modulator 120G along the Z direction through theanamorphic projection optical system 130G in the “on” mirror position,and directed outside of the anamorphic projection optical system 130S toa light absorbing beam stop 140G in the “off” mirror position. With thecomponents of imaging apparatus 200G positioned in this “folded”arrangement, portions of homogenous light 118A-G directed to spatiallight modulator 120G-1 from homogenous light generator 110G arereflected from each MEMs mirror mechanism 125G to anamorphic opticalsystem 130G-1 only when the mirrors of each MEMs mirror mechanism 125Gare in the “on” position (e.g., as described above with reference toFIG. 9(A)). That is, as indicated in FIG. 10, each MEMs mirror mechanism125G that is in the “on” position reflects an associated one of lightportions 118B-G1 at angle θ1 relative to the incident light direction,whereby modulated light portions 118B-G1 are directed by spatial lightmodulator 1200-1 along corresponding predetermined directions toanamorphic optical system 130G-1, which is positioned and arranged todirect concentrated light portions 118C-G1 onto scan line portion SL-1,where scan line portion SL-1 is perpendicular to the Z-axis defined bythe surface of spatial light modulator 120G-1 and the scan line SL-1 isparallel to the X-axis. Conversely, each MEMs mirror mechanism 125G thatis in the “off” position reflects an associated one of light portions118A-G at angle θ2, whereby modulated light portions 118B-G2 aredirected by spatial light modulator 120G away from anamorphic opticalsystem 130G-1. According to an aspect of the preferred “folded”arrangement, imaging apparatus 200G includes a beam stop heat sinkstructure 140G-1 that is positioned to receive modulated light portions118B-G2 that are reflected by MEMs mirror mechanisms 125G in the “off”position. According to another aspect of the preferred “folded”arrangement using the compound incident angle design set forth above,the components of imaging apparatus 200G are arranged in a manner thatfacilitates the construction of a seamless assembly including any numberof identical imaging systems, such as described below with reference toFIG. 13.

FIGS. 11 and 12 are simplified exploded and assembled perspective views,respectively, showing a portion of imaging apparatus 200H including thecomponents shown in FIG. 10, and further including a rigid frame 150Haccording to another embodiment of the present invention. The purpose offrame 150H is to facilitate low-cost assembly and to maintain the systemcomponents in the preferred “folded” arrangement (discussed above withreference to FIG. 10). In addition, as discussed below with reference toFIG. 13, the disclosed design of frame 150H facilitates forming a largerassembly.

Referring to FIG. 11, frame 150 k is a single piece structure that ismolded or otherwise formed from a suitable rigid material (e.g., a hardplastic such as polycarbonate, or a metal such as aluminum, andgenerally includes an angled base portion 151H defining a support area152H, a first arm 153H and a second arm 154H that extend from baseportion on opposite sides of support area 152H, a first box-like bracket155H integrally attached to an end of first arm 153H, a second box-likebracket 156H integrally attached to first bracket 155H, and a thirdbracket 157H attached to an end of second arm 153H. As indicated inFIGS. 11 and 12, support area 152H is shaped and arranged to facilitatemounting of DMD-type spatial light modulator 120G in a predeterminedorientation, and brackets 155H, 156H and 157H are positioned andoriented to receive operating ends of homogenous light generator 110G,anamorphic optical system 130G and heat sink 140G, respectively, suchthat these elements are properly oriented with DMD-type spatial lightmodulator 120G when fixedly secured thereto.

FIG. 13 is a simplified perspective view showing an apparatus/assembly200L made up of a series of three imaging subsystems 100H-1, 100H-2 and100H-3 that are stacked across the width of an imaging area (i.e., asurface coincident with or parallel to elongated scan line image SL-H)according to another embodiment of the present invention. Each imagingsubsystem 100H-1, 100H-2 and 100H-3 includes an associated frame 150H-1,150H-2 and 150H-3, an associated homogenous light source 110G-1, 110G-2and 110G-3 respectively attached to first brackets 155H-1, 155H-2 and155H-3 of each frame 150H-1, 150H-2 and 150H-3, an associated DMD-typespatial line modulator 120G-1, 120G-2 and 120G-3, an associatedanamorphic optical system 130G-1, 130G-2 and 130G-3, and an associatedheat sink 140G-1, 140G-2 and 140G-3 arranged in a manner consistent withthat described above with reference to FIGS. 11 and 12. Imagingsubsystems 100H-1, 100H-2 and 100H-3 are arranged such chat anamorphicoptical system 130G-1 to 130G-3 are fixedly connected in a side-by-sidearrangement, and such that scan line sections SL-1 to SL-3 aresubstantially collinear and form an elongated scan line SL-k on scanstructure 160.

Although apparatus 200L is shown with only three subsystems 100H-1,100H-2 and 100H-3, the illustrated arrangement clearly shows that thefolded arrangement described above with reference to FIGS. 10-12facilitates assembling any number of imaging systems to form a focal(scan) line having any length. That is, one advantage provided by thefolded arrangement of each subsystem associated with apparatus 200L isthat each optical subsystems 100H-1 to 100H-3 can be manufactured usingmass-produced, readily available components (e.g., DMD chips produced byTexas Instruments) so that each subsystem can benefit from pricereductions coming from volume manufacturing. There is currently nosingle spatial light modulator device that can be utilized in theimaging system of the present invention that has sufficient size togenerate a scan line of 20 inches or more in the cross process directionwith sufficient resolution (e.g., 1200 dots-per-inch). By producingmultiple optical subsystems (e.g., optical subsystems 100H-1 to 100H-3)using currently commercially available DMD-type spatial light modulatordevices, arranging the subsystem components using the folded arrangementdescribed herein, and stacking the subsystems in the manner shown inFIG. 13, an economical apparatus can be produced that provides a scanline of essentially any width.

A possible limitation to the imaging apparatus of the present inventiondescribed above is that particular spatial light modulators may notprovide sufficient scan line resolution. That is, the spatial lightmodulators of the various embodiments described above includearrangements in which the rows and columns of light modulating elementsare disposed orthogonal to the focal/scan line (i.e., such that thelight portions directed by all light modulating elements in each columnin the “on” position are summed on a single imaging region of thefocal/scan line). This orthogonal arrangement may present a problem whenthe desired resolution for a given application is greater than themodulating element resolution (i.e., the center-to-center distancebetween adjacent elements in a row) of a given spatial light modulator.For example, many photolithography printing applications requireresolutions of 1200 dpi or greater, but a standard DLP chip includes amirror array having 1024 columns of mirrors spaced at 13.68 μm whichforms 600 pixels per inch in the fast scan direction when using aprojection lens with a magnification of 3.0945, thereby limiting theresolution of an image system using the orthogonal arrangement to aresolution of 600 dpi.

FIG. 14 is a perspective view showing a portion of a single-pass imagingapparatus 200K according to another embodiment of the present inventionthat addresses the potential problems associated with the orthogonalarrangement set forth above. Similar to generalized imaging apparatus200 (discussed above with FIG. 1), imaging apparatus 200K generallyincludes homogenous light generator 110, a spatial light modulator120-1, an associated anamorphic optical (e.g., projection lens) system130-1 and a scan structure 160 that operate substantially as discussedabove. However, imaging apparatus 200K differs from the generalizedimaging system in that spatial light modulator 120-1 is tilted relativeto anamorphic optical system 130-1 such that the rows of modulatingelements 125 are aligned at an acute tilt angle β relative to scan lineSL-1, whereby the elements in each column are slightly displaced in thehorizontal (X-axis) direction such that anamorphic optical system 130-1focuses each modulated light portion onto an associated horizontallydisplaced sub-imaging region of elongated imaging region 167 of scanstructure 160. In the example shown in FIG. 4(A), elements 125-141 and125-143 are in the “on” modulated state, whereby homogenous lightportions 118A-141 and 118A-143 are passed as modulated light portions118B-141 and 118B-143 to anamorphic optical system 130-1, and elements125-111 and 125-133 and 125-142 are in the “off” modulated state,whereby their received homogenous light portions (e.g., 118A-142) areprevented from passing to anamorphic optical system 130-1. Due to thetilt angle β, concentrated light portions 118C-141 and 118C-143 aredirected by anamorphic optical system 130-1 onto sub-imaging regionsSL-141 to SL-143, respectively, of scan line region SL-4 (sub-imagingregion SL-142 remains “dark” due to the “off” state of element 125-142).

As indicated in FIG. 15, which is a simplified diagram depicting thetilted orientation of a top edge 121 of spatial light modulator 120-1and scan line portion SL-1 (which extends in the X-axis direction),according to an aspect of the present embodiment, tilt angle β isselected such that the centers of each modulating elements 125-111 to125-143 are equally spaced along the X-axis direction, whereby eachlight portion passed through each modulating elements 125-111 co 125-143is directed onto a corresponding unique sub-imaging region of scan lineportion SL-1. That is, tilt angle β is selected such that the centers ofeach modulating element 125-111 to 125-143 (indicated by vertical dashedlines) are separated by a common pitch P along scan line portion SL-1(e.g., the centers of modulating elements 125-141 and 125-142 and thecenters of modulating element 125-143 and 125-131 are separated by thesame pitch distance P). In one embodiment, in order to equalize thepitch distance P for all modulating elements of spatial light modulator120, tilt angle β is set equal to the arctangent of 1/n, where n is thenumber of modulating elements in each column (that is, for thesimplified example, n=3), giving a uniform pitch distance P that isequal to the R/n, where R is the modulating element resolutiondetermined by the center-to-center distance between adjacent modulatingelements in each row.

Referring again to FIG. 14, due to the tilted orientation of spatiallight modulator 120-1 relative to scan line portion SL-1, the centers ofmodulating elements 125-141 to 125-143 are sequentially shifted to theright along the X-axis direction (i.e., the center of modulating element125-141 is slightly to the left of the center of modulating element125-142, which in turn is slightly to the left of the center ofmodulating element 125-143). Referring to the upper right portion ofFIG. 14, the slight offset between the light modulating elements in eachcolumn causes anamorphic optical system 130 to focus the light portionsreceived from each light modulating element such that the light iscentered on an associated unique sub-imaging region of scan line portionSL-1. For example, light portions 118B-141 and 118B-143, which arepassed by modulating elements 125-41 and 125-43 to anamorphic opticalsystem 130-1, are focused and centered on sub-imaging regions SL-41 toSL-43. Note that overlap of light passed by modulating elements 125-141and 125-143 is ignored for explanatory purposes, and the slight offsetin the Y-axis direction is amplified for illustrative purposes. Thebenefit of this tilted orientation is that imaging apparatus 200Kproduces a higher resolution linear image than that possible using aright-angle orientation, and allows for sub-pixel spacingaddressability, and provides an opportunity to utilize soft ware toposition image “pixels” with fractional precision in both the X-axis andY-axis directions.

FIGS. 16 and 17 are simplified diagrams depicting a further portion ofapparatus 200K including spatial light modulators 120-1 and 120-2, bothbeing inclined at tilt angle β relative to associated scan line portionsSL-1 and SL-2. FIG. 16 is modified to illustrate the effectivepre-stitching overlap between light portions modulated by each of thevarious modulating elements (i.e., this overlap may be produced by theanamorphic projection optical systems, not shown, and not the physicaloverlap of spatial light modulators 120-1 and 120-2). In particular,light passing through spatial light modulator 120-1 forms imaged andconcentrated light beams 118C-1 (indicated by dash-dot lines) that aredirected onto scan structure 160 in the manner described above toproduce scan line portion SL-1, and light passing through spatial lightmodulator 120-2 forms imaged and concentrated light beams 118C-2(indicated by dash-dot-dot lines) that are directed onto scan structure160 to produce scan line portion SL-2. Due to the overlap arrangement,certain elements produce overlapping concentrated light 118C-OL thatgenerates redundant light spots on scan structure 160. For example,element 125-131 of spatial light modulator 120-1 is functionally aligned(overlapped with element 125-211 of spatial light modulator 120-2,element 125-143 of spatial light modulator 120-1 is functionally alignedwith element 125-211 of spatial light modulator 120-2, element 125-142of spatial light modulator 120-1 is functionally aligned with element125-213 of spatial light modulator 120-2, and element 125-141 of spatiallight modulator 120-1 is functionally aligned with element 125-221 ofspatial light modulator 120-2. A stitching control approach similar tothat discussed above can be implemented to address the overlap situationshown in FIG. 16 by turning off (disabling) elements in the overlappingsections, and redistributing the image data to match the overall phase.For example, as shown in FIG. 17, the image data is modified such thatmodulating elements 125-141 and 125-142 of spatial light modulator 120-1are effectively disabled, and the image data associated with thecorresponding location on scan structure 160 is directed to modulatingelements 125-221 and 125-213 of spatial light modulator 120-2. Inaddition, the image data is modified such that modulating elements125-211 and 125-212 of spatial light modulator 120-2 are effectivelydisabled, and the image data associated with the corresponding locationon scan structure 160 is directed to modulating elements 125-141 and125-142 of spatial light modulator 120-1. The resulting stitchedoperation of apparatus 200K eliminates the overlap such that allconcentrated light portions 118C-1 and 118C-2 are directed onto uniqueregions of scan structure 160.

FIG. 18 is a partial front view showing a portion of an imagingapparatus 200L including a simplified DMD-type spatial light modulator120L-1 that is inclined at a tilt angle βL relative to scan line SL-1generated by an associated anamorphic optical system 130L-1 according toanother specific embodiment of the present invention. Because exemplaryDMD-type spatial light modulator 120L-1 includes fifteen mirrors 125L ineach column, the range of possible tilt angles maybe selected from therange of 26.57° (i.e., the arctangent of ½) to 3.81° (i.e., thearctangent of 1/15). In the illustrated embodiment, tilt angle βL isapproximately 14.0° (i.e., the arctangent of ¼) in order to produce asub-pixel spacing of four pixels per column of mirrors. By adjusting thetilt angle βL between these two extremes, multiple mirrors 125L can bealigned with each imaging sub-region. For example, as indicated in FIG.18, this sub-pixel spacing aligns four mirror elements 125L-1 to 125L-4with an image sub-region SL-23 on scan line portion SL-1. Note thatmirror elements 125L-1 to 125L-4 are disposed in different columns ofDMD-type spatial light modulator 120L-1, and are aligned with imagesub-region SL-23 only because of tilt angle βL. Note also that adjacentimage pixels are slightly overlapped and provide extra addressability inthe fast scan direction so that vertical edges can be adjusted left orright in sub-pixel increments. For the process direction, timing can beadjusted to ensure that horizontal edges are delayed or advanced in timeto occur at a position where they are needed, also in sub-pixelincrements.

Variable resolution can be implemented by controlling the number ofmirror centers located within each imaging region. Referring to FIG. 15as an example where n=3, using three mirrors in a vertical row increasesthe image resolution by a factor of three. In contrast, if a tilt anglewere selected such that every four mirrors as in FIG. 18, a slightlysmaller tilt angle βL is used than that of the embodiment shown in FIG.15, producing a higher resolution. When n=786 (as in typical DLP chips),it is easy to see that a wide range of alternate resolutions could beimplemented with high precision.

Similar to the orthogonal arrangement described above, the tiltedorientation shown in FIG. 18 also facilitates variable power along scanline image SL. That is, to produce an image having a maximum power orbrightness at image sub-region SL-23, all of mirror elements 125L-1 to1251-4 may be toggled to the “on” position, and to produce an imagehaving a lower power at image sub-region SL-23, one or more of mirrorelements 125L-1 to 125L-4 may be toggled to the “off” position.Moreover, not all the DMD mirrors need be utilized for full powerperformance. One or more “reserve” mirrors can be saved (i.e.,deactivated) during normal operation, and utilized to replace amalfunctioning mirror or to increase power above the normal “full” powerduring special processing operations. Conversely, fewer mirrors can beused to decrease power in a particular image sub-region to correctintensity defects. By calibrating the number of mirrors available forablation as a function of scan position, the power can be kept uniformover the scan surface, and calibrated at will when off line.

Bow, tilt and process direction velocity imperfections such as bandingcan be also be controlled by the rate at which image lines and pixelsare modulated on the array. Speeding up or slowing down this processwill create higher or lower line resolution, respectively, or be used tocompensate for banding. Delaying or advancing segments of lines orpixels in sub-resolution increments can be used to compensate for bow ortilt over the scan line. Furthermore, this arrangement can also be usedto move horizontal edges of text, lineart, or dots for further processdirection control of the image to complete a general two-dimensionalhyperacidity printer capable of warping and registering images.

FIG. 19 is a simplified perspective view showing a scanning/printingapparatus 200M that includes single-pass imaging system 100M and a scanstructure (e.g., an imaging drum cylinder) 160M according to anotherembodiment of the present invention. As described above, imaging system100M generally includes a homogenous light generator 110M, a spatiallight modulator 120M, and an anamorphic optical (e.g., projection lens)system 130M that function essentially as set forth above. Referring toupper right portion of FIG. 19, imaging drum cylinder (roller) 160M ispositioned relative to image system 100M such that anamorphic opticalsystem 130M images and concentrates the modulated light portionsreceived from spatial light modulator 120M onto an imaging surface 162Mof imaging drum cylinder 160M, and in particular into an imaging region167M of imaging surface 162M, using a cross-process optical subsystem133M and a process-direction optical subsystem 137M in accordance withthe technique described above with reference to FIGS. 4(A) and 4(B). Ina presently preferred embodiment, cross-process optical subsystem 133Macts to horizontally invert the light passed through spatial lightmodulator 120M (i.e., such that light portions 118B-41, 118B-42 and118B-43 are directed from the right side of cross-process opticalsubsystem 133M toward the left side of imaging region 167M). Inaddition, in alternative embodiments, imaging drum cylinder 160M iseither positioned such that imaging surface 162M coincides with the scan(or focal) line defined by anamorphic optical system 130M, whereby theconcentrated light portions (e.g., concentrated light portions 118C-41,118C-42 and 118C-43) concentrate to form a single one-dimensional spot(light pixel) SL-4 in an associated portion of imaging region 167M, orsuch that imaging surface 162M is coincident with the focal line definedby anamorphic optical system 130M, whereby the light portions form aswath containing a few imaging lines (i.e., such that the lightsub-pixel formed by light portion 118C-41 is separated from the lightsub-pixel formed by light portion 118C-43. In a presently preferredembodiment, as indicated by the dashed-line bubble in the upper rightportion of FIG. 15, which shows a side view of imaging drum cylinder160M, imaging surface 162M is set at the focal line FL location suchthat the image generated at scan line SL-4 by beams 118C-41, 118C-42 and118C-43 is inverted in the fashion indicated in the dashed-line bubble.Additional details regarding anamorphic optical system 130M aredescribed in co-owned and co-pending application Ser. No. ______ [AttyRef. No. 20100876-US-NP (XCP-160)], entitled ANAMORPHIC PROJECTIONOPTICAL SYSTEM FOR HIGH SPEED LITHOGRAPHIC DATA IMAGING, which isincorporated herein by reference in its entirety.

FIGS. 20(A) and 20(B) are simplified perspective views showing portionsof imaging apparatus 200N and 200P according to alternative embodimentsof the present invention. Each of these figures shows the wedge-shapedlight beam fields 118C-1 to 118C-4 generated by associated imagingsystems (which are shown as blocks to simplify the diagram and areunderstood to include a spatial light modulator and an associatedanamorphic optical system), and a portion of an imaging drum cylinder onwhich the beam fields form associated scan line portions SL1-SL4, whichcollectively form a scan line SL in the manner described above. Imagingapparatus 200N and 200P are similar in that imaging systems 100N-1 to100N-4 generate and direct wedge-shaped light beam fields 118C1 to118C-4 onto surface 162N of imaging drum cylinder 160N to form scan lineSL (see FIG. 20(A)), and imaging systems 100P-1 to 100P-4 generate anddirect wedge-shaped light beam fields 118C1- to 118C-4 onto surface 162Pof imaging drum cylinder 1602 to form scan line SL (see FIG. 20(B).Imaging apparatus 200N and 200P differ in that imaging systems 100N-1 to100N-4 are arranged in an aligned pattern (e.g., using the techniquesdescribed above with reference to FIGS. 11-13), whereas imaging systems100P-1 to 100P-4 are arranged in an offset pattern. That is, imagingsystems 100P-1 to 100P-4 are arranged in two parallel rows, with imagingsystems 100P-1 and 100P-3 aligned in the first row and imaging systems100P-1 and 100P-3 aligned in the second row, where each imaging systemor each row includes an associated homogenous light source. Because allof imaging systems 100P-1 to 100P-4 are oriented to generate scan lineSL, wedge-shaped light beam fields 118C-1 to 118C-4 are directed ontosurface 162P from two different directions in an interlaced featheredmanner and are separated by a shallow angle. This offset patternarrangement provides more room between adjacent imaging systems 100P-1to 100P-4 than that provided by the aligned arrangement of imagingapparatus 200N (FIG. 20(A)).

Although the present invention has been described with respect tocertain specific embodiments, it will be clear to those skilled in theart that the inventive features of the present invention are applicableto other embodiments as well, all of which are intended to fall withinthe scope of the present invention. For example, although the presentinvention is illustrated as having light paths that are linear (seeFIG. 1) or with having one fold (see FIG. 10), other arrangements may becontemplated by those skilled in the art that include folding along anynumber of arbitrary light paths.

1. A method for generating a substantially one-dimensional scan lineimage in response to received image data, the method comprising:generating homogenous light such that the homogenous light forms one ormore substantially uniform two-dimensional homogenous light fields;separating the received image data into two or more portions such that afirst image data portion of the image data corresponds to a first scanline portion of the scan line image, and a second image data portion ofthe image data corresponds to a first scan line portion of the scan lineimage; controlling first and second pluralities of modulating elementsusing the first and second image data portions, each of the first andsecond pluralities of modulating elements being disposed in atwo-dimensional array in the one or more homogenous light fields,wherein each modulating element of the first plurality of modulatingelements is individually controlled by the first image data portion togenerate first modulated light forming a first two-dimensional modulatedlight field, and wherein each modulating element of the second pluralityof modulating elements is individually controlled by the second imagedata portion to generate second modulated light forming a secondtwo-dimensional modulated light field; and anamorphically imaging andconcentrating the first modulated light portions and the secondmodulated light portions such that the anamorphically imaged andconcentrated first modulated light portions generate a first scan lineportion and the anamorphically imaged and concentrated second modulatedlight portions generate a second scan line portion, and such that thefirst and second scan line portions collectively form at least a portionof said substantially one-dimensional scan line image.
 2. The methodaccording to claim 1, wherein the first plurality of light modulatingelements are arranged in a plurality of rows and a plurality of columns,wherein each said column includes an associated group of said firstplurality of light modulating elements, wherein controlling the firstplurality of modulating elements comprises adjusting each modulatingelement of the first plurality of modulating elements into one of afirst modulated state, in which said each modulating element modulatesan associated received homogenous light portion of said homogenous lightsuch that an associated modulated light portion is directed in acorresponding predetermined direction, and a second modulated state inwhich said each modulating element modulates the associated receivedhomogenous light portion such that the associated modulated lightportion is prevented from passing along said corresponding predetermineddirection, and wherein anamorphically concentrating the first modulatedlight portions comprises concentrating said first modulated lightportions received from each associated group of said first plurality oflight modulating elements of each said column onto an associated imagingregion of said first scan line portion.
 3. The method according to claim2, wherein separating the received image data comprises modifying atleast one of said first image data portion and said second image dataportion such that an associated group of said plurality of lightmodulating elements forming a column of at least one of said first andsecond pluralities of light modulating elements is disabled, wherebyadjacent end portions of the first and second scan line portions arealigned in a scan direction to produce a seamlessly stitched portion ofsaid single-pass scan line.
 4. The method according to claim 3, whereinseparating the received image data further comprises further modifyingat least one of said first image data portion and said second image dataportion such that a feature spanning said seamlessly stitched portion ofsaid single-pass scan line is aligned in a cross-scan direction.
 5. Themethod according to claim 1, wherein generating homogenous lightcomprises generating one or more light beams having a first fluxdensity, and homogenizing said one or more light beams to produce saidhomogenized light having a second flux density, wherein the first fluxdensity is greater than the second flux density.
 6. The method accordingto claim 1, wherein anamorphically imaging and concentrating the firstmodulated light portions comprises: projecting and magnifying said firstmodulated light portions in a cross-process direction using first andsecond focusing lens, and concentrating said first modulated lightportions in a direction parallel to a process direction using a thirdfocusing lens.
 7. The method according to claim 1, wherein controllingthe first plurality of modulating elements comprises transmitting thefirst image data portion to one of a digital micromirror device, anelectro-optic diffractive modulator array, and an array of thermo-opticabsorber elements.
 8. The method according to claim 1, wherein the firstplurality of modulating elements comprises a plurality ofmicroelectromechanical (MEMs) mirror mechanisms disposed on a substrate,and wherein controlling the first plurality of modulating elementscomprises individually controlling the plurality of MEMs mirrormechanisms such that a mirror of each said MEM mirror mechanism is movedbetween a first tilted position relative to the substrate, and a secondtilted position relative to the substrate in accordance with said firstimage data portion.
 9. The method according to claim 8, whereincontrolling the first plurality of modulating elements further comprisespositioning each of the plurality of MEMs mirror mechanisms such that,when the mirror of each said MEMs mirror mechanism is in the firsttilted position, said mirror reflects an associated homogenous lightportion of said homogenous light such that said reflected light portionis directed to an anamorphic optical system, and when said mirror ofeach said MEMs mirror mechanism is in the second tilted position, saidmirror reflects said associated received homogenous light portion suchthat said reflected light portion is directed away from the anamorphicoptical system.
 10. The method according to claim 9, further comprisingpositioning a heat sink relative to the plurality of MEMs mirrormechanisms such that when said mirror of each said MEMs mirror mechanismis in the second tilted position, said reflected light portion isdirected onto said heat sink.
 11. The method according to claim 1,further comprising positioning the first and second pluralities ofmodulating elements in an offset arrangement and anamorphically imagingand concentrating the first and second modulated light portions suchthat the anamorphically imaged and concentrated first modulated lightportions form an interlaced feathered arrangement.
 12. A method forgenerating a single-pass scan line in an elongated imaging region inresponse to received image data, the method comprising: transmittinghomogenous light onto first and second spatial light modulators, each ofthe first and second spatial light modulators including a plurality oflight modulating elements arranged in a two-dimensional array anddisposed such that each said modulating element receives an associatedportion of the homogenous light; separating the received image data intotwo or more portions such that a first image data portion of the imagedata corresponds to a first scan line portion of the scan line image,and a second image data portion of the image data corresponds to a firstscan line portion of the scan line image; individually controlling theplurality of modulating elements of each of the first and second spatiallight modulators in accordance with the first and second image dataportions such that each modulating element is adjusted between a firstmodulated state and a second modulated state, wherein when said eachmodulating element is in said first modulated state, said eachmodulating element directs said associated received light portion in acorresponding predetermined direction, and when said each modulatingelement is in said second modulated state, said associated receivedlight portion is prevented from passing along said correspondingpredetermined direction by said each modulating element; andanamorphically imaging and concentrating the first modulated lightportions from said first spatial light modulator and the secondmodulated light portions from said second spatial light modulator suchthat the anamorphically imaged and concentrated first modulated lightportions generate a first scan line portion on the elongated imagingregion and the anamorphically imaged and concentrated second modulatedlight portions generate a second scan line portion on the elongatedimaging region, wherein the received image data is modified such thatadjacent end portions of the first and second scan line portions producea seamlessly stitched portion of said single-pass scan line.
 13. Themethod according to claim 12, wherein the first plurality of lightmodulating elements are arranged in a plurality of rows and a pluralityof columns, wherein each said column includes an associated group ofsaid first plurality of light modulating elements, and whereinanamorphically imaging and concentrating the first modulated lightportions comprises imaging and concentrating said first modulated lightportions received from each associated group of said first plurality oflight modulating elements of each said column onto an associated imagingregion of said first scan line portion.
 14. The method according toclaim 13, wherein separating the received image data comprises modifyingat least one of said first image data portion and said second image dataportion such that an associated group of said plurality of lightmodulating elements forming a column of at least one of said first andsecond pluralities of light modulating elements is disabled, wherebyadjacent end portions of the first and second scan line portions arealigned in a scan direction to produce said seamlessly stitched portionof said single-pass scan line.
 15. The method according to claim 14,wherein separating the received image data further comprises furthermodifying at least one of said first image data portion and said secondimage data portion such that a feature spanning said seamlessly stitchedportion of said single-pass scan line is aligned in a cross-scandirection.
 16. The method according to claim 12, wherein generatinghomogenous light comprises generating one or more light beams having afirst flux density, and homogenizing said one or more light beams toproduce said homogenized light having a second flux density, wherein thefirst flux density is greater than the second flux density.
 17. Themethod according to claim 12, wherein anamorphically imaging andconcentrating the first modulated light portions comprises: projectingand magnifying said first modulated light portions in a cross-processdirection using first and second focusing lens, and imaging andconcentrating said first modulated light portions in a directionparallel to a process direction using a third focusing lens.
 18. Themethod according to claim 12, wherein individually controlling the firstplurality of modulating elements comprises transmitting the first imagedata portion to one of a digital micromirror device, an electro-opticdiffractive modulator array, and an array of thermo-optic absorberelements.
 19. The method according to claim 12, wherein the firstplurality of modulating elements comprises a plurality ofmicroelectromechanical (MEMs) mirror mechanisms disposed on a substrate,and wherein individually controlling the first plurality of modulatingelements comprises individually controlling the plurality of MEMs mirrormechanisms such that a mirror of each said MEM mirror mechanism is movedbetween a first tilted position relative to the substrate, and a secondtilted position relative to the substrate in accordance with said firstimage data portion.
 20. The method according to claim 19, whereinindividually controlling the first plurality of modulating elementsfurther comprises positioning each of the plurality of MEMs mirrormechanisms such that, when the mirror of each said MEMs mirror mechanismis in the first tilted position, said mirror reflects an associatedhomogenous light portion of said homogenous light such that saidreflected light portion is directed to an anamorphic optical system, andwhen said mirror of each said MEMs mirror mechanism is in the secondtilted position, said mirror reflects said associated receivedhomogenous light portion such that said reflected light portion isdirected away from the anamorphic optical system.
 21. The methodaccording to claim 20, further comprising positioning a heat sinkrelative to the plurality of MEMs mirror mechanisms such that when saidmirror of each said MEMs mirror mechanism is in the second tiltedposition, said reflected light portion is directed onto said heat sink.